1. Field of the Invention
The present invention relates to a sensor system for determining the moisture content of a fluid medium flowing in a main flow direction.
2. Description of the Related Art
Numerous methods and devices for determining at least one property of a flowing fluid medium, that is, liquids and/or gases, are known from the related art. The properties, as possible parameters, may basically be any physically and/or chemically measurable properties which qualify or quantify a flow of the fluid medium, in this context. In particular, this may be about a flow speed and/or a mass flow and/or a volume flow. One further property of the flowing fluid medium is the moisture content.
The field of the present invention will be described below, particularly with reference to so-called moisture sensors, as described, for example, in Konrad Reif (Edtr.): Sensors in the Motor Vehicle, 1st edition 2010, pages 98-101.
Such a moisture sensor may be situated in a housing of its own sensor system or in a housing of a so-called hot-film air-mass sensor. Such a setup is described, for example, in German patent application document DE 10 2010 043 062 A1. In this case, the moisture sensor is accommodated in the sensor housing of the hot-film air mass sensor. The sensor housing has an inlet opening for the moisture which is closed by a semipermeable membrane. The moisture penetrates the membrane and thereby reaches the moisture sensor on the inside of the sensor housing. The membrane is provided to retain dirt particles, in this context.
Despite the numerous advantages of the methods and devices, known from the related art for detecting the moisture content, they still include room for improvement. The danger in the above systems is that the membrane of the moisture sensor may be contaminated during operation by water, dust or oil mist, for example. This causes less moisture to reach the moisture sensor than in the case of an uncontaminated membrane. This is able to lead to errors in the determination of the moisture content.